JP2019190687A - Biomass combustion method and combustion apparatus - Google Patents

Abstract

To provide a biomass combustion method and a combustion apparatus capable of suppressing fusion and agglomeration of fluidized particles in a fluidized bed of a fluidized bed furnace and stably burning high potassium-containing biomass such as herbaceous biomass.SOLUTION: In a combustion method for supplying biomass to a furnace body 10 of a fluidized bed furnace 1, supplying oxidizing gas from the lower part of the furnace body 10, causing the biomass to flow together with fluidized particles to form a fluidized bed and burning the biomass in the fluidized bed, pyrolysis residue molten slag generated by melting and then, cooling pyrolysis residues of waste in a waste gasification melting furnace or ash molten slag generated by melting and then, cooling ash of the waste in an ash melting furnace is used as the fluidized particles.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a biomass combustion method and combustion apparatus for burning biomass in a fluidized bed in which fluidized particles are fluidized with an oxidizing gas in a furnace body of a fluidized bed furnace. In particular, the present invention relates to a combustion method and combustion apparatus for high potassium-containing biomass such as herbaceous biomass.

  In recent years, the use of biomass energy has attracted attention as a measure to prevent global warming. Biomass is a renewable organic resource, not a fossil resource, so it can be regenerated. Among these, plant-derived biomass is particularly expected to have an effect of reducing carbon dioxide emissions.

  Since biomass is an organic substance, carbon dioxide is generated when it is burned. Plant-derived biomass contains carbon resources that are converted from carbon dioxide by photosynthesis during the growth of the plant. In short, the carbon dioxide generated by the combustion of plant-derived biomass is derived from the carbon dioxide absorbed by the plant from the atmosphere during the growth process. Therefore, even if biomass is burned, it can be considered that the amount of carbon dioxide in the atmosphere is not increased as a whole. That is, biomass is a carbon neutral energy source. As such plant-derived biomass, herbaceous biomass, particularly oil palm empty fruit bunch and switchgrass, has attracted attention.

  The empty fruit bunch of oil palm is the part that remains after collecting palm oil from the fruit of oil palm. The oil palm fruit bunch has hundreds of fruits with a diameter of several centimeters, and the fruit is strongly bound to the core of the fruit bunch. In order to weaken this bond and easily separate the fruit from the core, the fruit bunches are first steam-heated in order to further suppress alteration of the oil extraction component. Thereafter, the fruit is removed by a rotary sieve or the like. The remaining portion from which the fruit is removed is an empty fruit bunch (EFB). Although empty fruit bunches are discharged in large quantities but contain a lot of water, they have been discarded without being used effectively or left open.

  In recent years, attempts have been made to use the oil palm empty fruit bunch as boiler fuel, and an apparatus for that purpose has been proposed. Such an apparatus is a steam-heated fruit-removing machine that separates fruits from an empty fruit bun with a rotary sieve under steam pressure, an empty fruit buncher that cuts the empty fruit bun after the fruit removal, and a squeezed empty fruit bun after the cutting. Equipped with empty fruit bunch press. The empty fruit bunch is cut by an empty fruit bunch cutting machine, and then water is removed by an empty fruit bunch press and used as boiler fuel.

  Switchgrass is a perennial gramineous plant that grows significantly faster, and the use of stems as fuel is being studied.

  As a specific technique for using such herbaceous biomass as boiler fuel, a particulate fluid medium (hereinafter referred to as “fluid particles”) supplied into the furnace is supplied with oxidizing gas from the lower part of the furnace. A method of using a fluidized bed furnace in which biomass is burned in a fluidized bed that has been fluidized has been studied. In a fluidized bed furnace, inexpensive and general-purpose silica sand particles are often used as fluidized particles.

  Patent Document 1 discloses a circulating fluidized bed furnace for burning a processing object such as sludge and waste instead of herbaceous biomass. The circulating fluidized bed furnace of Patent Document 1 is mainly composed of a riser as a furnace body and a downcomer that collects fluidized particles and returns them to the riser, and the downcomer is connected to the upper part of the riser by a connecting pipe. A collecting unit for collecting the flowing particles sent from the riser together with the exhaust gas, a return pipe for returning the flowing particles collected by the collecting unit to the lower part of the riser, and a gas from the riser collecting It has a seal part which prevents rising in the part.

  In the circulating fluidized bed furnace, the primary air is supplied upward from the lower part of the riser and the secondary air is supplied from the side part of the riser, and the object to be treated put into the riser together with fluid particles such as sand. By flowing, a fluidized bed is formed in the riser. The object to be treated is combusted in the fluidized bed, and the exhaust gas generated in the riser and a part of the fluidized particles are sent to the downcomer for solid-gas separation. The exhaust gas is discharged from the collection unit to an external exhaust gas treatment facility. In addition, the fluidized particles are collected by the collecting unit, descend, and returned to the riser through the return pipe.

  Herbaceous biomass such as oil palm empty fruit bunches, switchgrass, bamboo and rice husks are rich in potassium. For example, the potassium content in herbaceous biomass is about 0.7 to 3 wt% on a dry basis. Therefore, when high-potassium-containing biomass such as herbaceous biomass is treated as an object to be processed, for example, in a fluidized bed furnace such as a circulating fluidized bed furnace disclosed in Patent Document 1, combustion heat energy is recovered due to this potassium. The following problems arise.

When the silica sand particles are fluidized particles, in the fluidized bed furnace, gaseous potassium compounds released from the herbaceous biomass by combustion are adsorbed on the silica sand particle surfaces, and the SiO ₂ -K ₂ O compound is adsorbed on the silica sand particle surfaces. Since the melting temperature of this substance is lower than the temperature in the fluidized bed furnace, a melted material is formed on the surface of the silica sand particles. As a result, the silica sand particles are fused together, causing the silica sand particles to aggregate and agglomerate (referred to as “agglomeration”), and the fluidized state of the silica sand particles cannot be maintained. Driving is hindered.

  If herbaceous biomass is put into a fluidized bed where fluidized particles are agglomerated and agglomerated and are not in good flow, the herbaceous biomass cannot be evenly dispersed in the fluidized particles and burns in a partially collected state. It will not be able to burn evenly. As a result, the heat generating region is unevenly distributed in the furnace, and a hot spot that is a local high-temperature portion is formed. Therefore, generation of harmful gases such as NOx and fire resistance in the furnace Problems such as damage to objects, shortening of useful life, generation of CO, and the like occur, and stable combustion of herbaceous biomass becomes difficult.

  In addition, when there is a risk of fluid particles agglomerating, in order to maintain a fluid state, it is necessary to frequently perform operations of exchanging fluid particles by extracting a large amount of fluid particles and replenishing new fluid particles. For this reason, there arises a problem that it cannot be operated continuously and a problem that a large amount of cost is required to purchase new fluid particles and to discard the fluid particles extracted.

  Patent Document 2 discloses a herbaceous biomass combustion method that can suppress the aggregation of fluidized particles and stably burn herbaceous biomass in a fluidized bed of a fluidized bed furnace. Has been. In Patent Document 2, the following examination is made.

  In order to investigate the cause of the fusion and aggregation of fluid particles, various types of biomass, namely wood chips, PKS (residues squeezed from oil palm seeds), EFB (oil palm empty fruit bunches), and switchgrass ash are analyzed and ash content is analyzed. The potassium content in the dry biomass was determined from the analysis result of the potassium content in the dry biomass.

  Among biomass, EFB (oil palm empty fruit bunch) and switching glass contain about 0.7 to 3 wt% of potassium on a dry basis. Next, the behavior of silica sand particles when burning such high-potassium-based herbaceous biomass in a circulating fluidized bed furnace is examined in detail, and the herbaceous biomass causes fusion to the silica sand particles. It was found that the mechanism was as follows.

The herbaceous biomass charged into the circulating fluidized bed furnace burns and releases gaseous potassium compounds in the combustion zone of the furnace body. The surface of the silica sand particles coexisting in the combustion region adsorbs this potassium compound, and potassium penetrates into the crystal of the silica sand particles to form a glassy reaction product (SiO ₂ -K ₂ O compound), and the reaction generated Since the melting point of the product is 800 ° C. or lower, which is lower than the furnace temperature, it becomes a molten state. The sand grains potassium had penetrated since SiO 2 _-K 2 _O compound in a molten state on the surface is generated have fusion-bonded silica sand grains few grains of fused and aggregation. The fused and agglomerated silica sand particles fall to the furnace bottom of the furnace body and are further fused and agglomerated to form a lump. Such a fusion and aggregation phenomenon of silica sand particles is called “agglomeration”. In this way, it was found that in the herbaceous biomass, the released potassium compound generates a molten reactant on the surface of the fluidized particles, and the fluidized particles are fused. In addition, when burning waste other than herbaceous biomass in a fluidized bed furnace, there are cases where the combustion ash melts and fluidized particles are fused by the combustion ash, but the combustion ash of herbaceous biomass does not reach the furnace temperature. Since it does not melt and is discharged from the furnace main body together with the gas as fly ash, the combustion ash does not cause fusion of the fluidized particles.

  Patent Document 3 reports that the use of smelting slag such as ferronickel slag having a high magnesium content as fluidized particles (fluidized particles) can suppress the generation of low melting point compounds.

JP 2003-240209 A JP2013-029245 International Publication 2011-007618

  However, there are only a few of the slags that are available as by-products, such as smelting slag such as ferronickel slag, that contain magnesium, and many of them are difficult to obtain and are used as fluidized particles in a fluidized bed furnace. Often unsuitable for.

  The present invention has been made in view of such circumstances, and suppresses fusion / aggregation of fluidized particles in a fluidized bed of a fluidized bed furnace, and stably burns high potassium-containing biomass such as herbaceous biomass. It is an object of the present invention to provide a biomass combustion method and a combustion apparatus capable of performing the above.

  According to the present invention, the above-described problems are solved by the biomass combustion method according to the first invention and the biomass combustion apparatus according to the second invention.

<First invention>
The biomass combustion method according to the first aspect of the present invention is to supply a biomass to a furnace body of a fluidized bed furnace and supply an oxidizing gas from a lower part of the furnace body to flow the biomass together with fluidized particles to form a fluidized bed. And burning the biomass in the fluidized bed.

  In this combustion method, in the first invention, the pyrolysis residue melting slag produced by melting the pyrolysis residue of the waste in the waste gasification melting furnace and then cooling, or the ash of waste in the ash melting furnace An ash melt slag produced by melting and then cooling is used as fluidized particles.

The biomass burned by the combustion method of the first invention is a high potassium-containing biomass such as herbaceous biomass in particular. Pyrolysis residue molten slag or ash molten slag used as fluidized particles in this combustion method (hereinafter collectively referred to as “molten slag” when it is not necessary to distinguish them) is composed mainly of silicon oxide (SiO), oxidized Calcium (CaO) and about 10 to 30 wt% alumina (Al ₂ O ₃ ). Since the molten slag contains calcium oxide (CaO), as described later, the molten slag is suitable as fluidized particles for preventing agglomeration when burning herbaceous biomass.

As described above, the molten slag contains calcium oxide (CaO) as well as silicon oxide (SiO) in its components. By using molten slag as fluidized particles in a fluidized bed furnace, the calcium compound fine particles desorbed from the molten slag fluidized particles coexist in the furnace from which the potassium compound is released from the herbaceous biomass. Then, it adheres to the surface of the molten slag fluidized particles containing silicon oxide that has begun to produce a melt in the presence of a potassium compound, and a reaction product containing a SiO ₂ —K ₂ O—CaO compound as a main component is produced. The reaction product is a high-melting-point material whose melting point is higher than the furnace temperature and does not enter a molten state. (Melation) can be prevented.

In the first invention, pyrolysis residue molten slag or ash molten slag whose basicity (CaO / SiO ₂ weight ratio in slag) is adjusted to 1.0 to 2.0 may be used as fluidized particles.

  The strength characteristic of the molten slag is correlated with the composition component ratio. A multi-element solid solution such as molten slag has a different crystal structure depending on the composition ratio, and the strength varies greatly. Therefore, by adjusting the basicity, in other words, the composition component ratio, it is possible to obtain a molten slag having a strength suitable as a fluidized particle.

  When the basicity of the molten slag is less than 1.0, the strength of the molten slag is low, and it is not suitable because it collapses or wears when used as a fluidized particle. When the basicity of the molten slag is more than 2.0, Since crystallinity falls and intensity | strength falls, it is not preferable. Therefore, it is preferable to adjust the basicity of the molten slag used as fluidized particles to 1.0 to 2.0.

In the first invention, pyrolysis residue molten slag or ash molten slag whose basicity (CaO / SiO ₂ weight ratio in the slag) is adjusted to 1.2 to 1.5 may be used as the fluidized particles.

  When the basicity of the molten slag is 1.2 or more, the crystallinity of the molten slag becomes high and the strength becomes sufficiently high, and the optimum strength as fluidized particles can be secured. Further, when the basicity of the molten slag is higher than 1.5, the melt viscosity of the molten slag becomes high, so that the molten slag flows to the extent that it can be discharged from the discharge port of the waste gasification melting furnace or ash melting furnace. Therefore, it is necessary to reduce the melt viscosity of the slag by setting the molten slag discharge temperature (slag temperature) to 1500 ° C. or higher. As a result, the temperature around the discharge port is increased, the wear of the refractory is increased, and in order to granulate the excessively high temperature slag into a good particle shape, Problems arise due to the need for action. Thus, it is not preferable that the basicity of the molten slag is larger than 1.5 in terms of the amount of molten slag discharged or water-ground. Therefore, it is more preferable to adjust the basicity of the molten slag used as fluidized particles to 1.2 to 1.5.

  In the first invention, when the pyrolysis residue molten slag is used as fluidized particles, the basicity of the pyrolysis residue melt slag is adjusted by adjusting the supply amount of limestone to be supplied together with the waste in the waste gasification melting furnace. It is good also as adjusting.

  In the first invention, when using ash molten slag as fluidized particles, the base of the ash molten slag is adjusted by adjusting the supply amount of quick lime or limestone that is supplied together with the incinerated ash to be melted in the ash melting furnace. The degree may be adjusted.

  Further, in the first invention, when using ash molten slag as fluidized particles, limestone collected with fly ash by a dust collector and blown into the exhaust gas for removal of acidic gas in the exhaust gas from the incinerator or It is good also as adjusting the basicity of a molten slag by supplying the alkaline fly ash containing slaked lime with the incinerated ash which is a melting process target in an ash melting furnace, and operating the supply amount of the said alkaline fly ash.

  Thus, by adjusting the basicity of the molten slag by adjusting the supply amount of limestone, quicklime and alkali fly ash in the waste gasification melting furnace or ash melting furnace, the Ca content and strength of the molten slag can be increased. The molten slag can be effectively used as fluidized particles within an appropriate range.

<Second invention>
The biomass combustion apparatus according to the second invention is supplied with biomass and supplied with an oxidizing gas from the lower part to flow the biomass together with fluidized particles to form a fluidized bed. It has a furnace body of a fluidized bed furnace for burning.

  In such a combustion apparatus, in the second invention, the fluidized particles are supplied to a pyrolysis residue melting slag generated by melting a pyrolysis residue of waste in a waste gasification melting furnace or cooling, or an ash melting furnace. It is characterized by ash-melting slag produced by melting and then cooling waste ash.

In such a combustion apparatus, the first invention has already been described by using the above pyrolysis residue molten slag or ash molten slag (hereinafter sometimes referred to as molten slag) as fluidized particles in a fluidized bed furnace. Similarly, a reaction product (high melting point material) mainly composed of a SiO ₂ —K ₂ O—CaO compound is generated on the surface of the molten slag medium particles to prevent fusion and aggregation (agglomeration) between the fluid particles. Is done.

In the present invention, by using molten slag as fluidized particles in a fluidized bed furnace, calcium compound fine particles desorbed from the molten slag fluidized particles are coexisted in a furnace in which potassium compounds are released from biomass, A reactant having a SiO ₂ —K ₂ O—CaO compound as a main component is generated by adhering to the surface of fluidized particles containing silicon oxide. The reactant is a high-melting-point material, the melting point is higher than the furnace temperature, and there is no melt on the surface of the fluidized particles, so that fusion / aggregation between the fluidized particles can be prevented. Therefore, since the fluidized particles do not agglomerate at the bottom of the furnace body, the fluidized particles flow well, the normal operation of the fluidized bed furnace can be maintained, and the biomass can be combusted stably. In addition, problems such as generation of harmful gases such as NOx, damage to refractories in the furnace, shortening of the service life, generation of CO, and the like due to hot spots that are local high-temperature portions can be avoided.

It is a schematic block diagram of the biomass combustion apparatus which concerns on embodiment of this invention. It is a state diagram illustrating the composition and the melting point temperature of SiO ₂ -K ₂ O-CaO compound.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram of a biomass combustion apparatus according to the present embodiment. The combustion apparatus has a circulating fluidized bed furnace 1. The circulating fluidized bed furnace 1 combusts biomass supplied into the furnace body in a fluidized bed in which fluidized particles (fluidized particles) are flowed by an oxidizing gas in the furnace body. In this embodiment, oil palm empty fruit bunches (EFB), which are herbaceous biomass, are supplied as biomass. Moreover, molten slag is used as the fluidized particles. In the present embodiment, the molten slag is a thermally decomposed residue molten slag generated by melting a thermally decomposed residue of waste in a waste gasification melting furnace and then cooling it. The main components of the molten slag are silicon oxide (SiO), calcium oxide (CaO), and about 10 to 30 wt% alumina (Al ₂ O ₃ ).

  In the present embodiment, an example in which the biomass is an oil palm empty fruit bunch will be described. However, the biomass is not limited to this, for example, biomass having a high potassium content such as switchgrass, bamboo, rice husk etc. (potassium content in dry biomass) For example, 0.7% or more). Moreover, the molten slag as fluidized particles may be included in part of the fluidized particles.

  As shown in FIG. 1, the circulating fluidized bed furnace 1 mainly includes a riser 10 as a furnace body and a downcomer 20 that collects a part of the fluidized particles and returns them to the riser 10. The downcomer 20 is connected to the upper portion of the riser 10 by a connecting pipe 30 and collects the flowing particles sent from the riser 10 together with the exhaust gas, and the flow collected by the collecting portion 21. It has a return pipe 22 for returning particles to the lower part of the riser 10 and a seal part 23 for preventing gas from the riser 10 from rising in the collection part 21.

  The riser 10 is provided with a diffuser tube 11 for directing the primary air upward, at the lower part in the furnace. Further, a supply port 13 for supplying an oil palm empty fruit bunch as fuel into the furnace and a secondary air injection port 12 for blowing secondary air into the furnace are provided at the lower side wall of the riser 10. Are provided sequentially.

By using molten slag as the fluidized particles in the fluidized bed furnace, the calcium compound fine particles desorbed from the molten slag fluidized particles coexist in the riser 10 from which the potassium compound is released from the empty palm bunch. Become. Then, the fine particles adhere to the surface of the molten slag fluidized particles containing silicon oxide that has started to melt in the presence of the potassium compound, and as a result, a reaction product mainly composed of the SiO ₂ —K ₂ O—CaO compound is obtained. Generated. The reactant is a high-melting-point material, and has a melting point higher than the furnace temperature and is present in the molten state on the surface of the molten slag flowing particles, so that a low-melting compound derived from potassium is not produced. Accordingly, since there is no melt on the surface of the fluidized particles, fusion and aggregation (agglomeration) between the fluidized particles are prevented.

  As described above, the molten slag used as fluidized particles in this embodiment is a pyrolysis residue molten slag generated in a waste gasification melting furnace. In a waste gasification and melting furnace that performs normal waste treatment operations, the basicity of the molten slag was 0.4 to 1.0 and the output temperature was operated at 1350 ° C. or lower. The slag of the degree is low in strength and cannot be applied as fluidized particles. In this embodiment, in order to obtain molten slag that can be used as fluidized particles, the basicity is adjusted by operating as follows.

  In this embodiment, the molten slag used as fluidized particles is adjusted so that its basicity will be described later by adjusting the amount of limestone supplied together with the waste in the waste gasification melting furnace. ing. Specifically, in a waste gasification melting furnace, to increase the limestone supply amount to increase the basicity, and to increase the molten slag discharge temperature in response to the increase in viscosity accompanying the increase in the basicity of the molten slag , Increase the coke supply rate and oxygen flow rate of oxygen-enriched air blown from the main tuyere, promote coke combustion, raise the molten slag temperature, lower the viscosity of the molten slag, and have a composition suitable for flowing particles ( The molten slag adjusted to basicity) can be discharged smoothly. Also, since the melting point of the molten slag increases by adjusting the basicity of the molten slag, in order to smoothly discharge the slag, the slag discharge temperature (steaming temperature) is set to 1350 ° C. or higher in response to the increase in the melting point. To do. Then, the discharged molten slag is dropped into a water tank and granulated or air cooled, and the particle size of the cooled slag is adjusted by grinding treatment to produce molten slag particles having a preferable particle size range.

  As described above, in the waste gasification melting furnace, the supply amount of limestone supplied together with the waste can be adjusted, the basicity of the slag can be adjusted, and the strength of the slag can be sufficiently increased. Can be used effectively.

  In the present embodiment, the basicity of the molten slag is adjusted to 1.0 to 2.0, more preferably 1.2 to 1.5. By setting the basicity of the molten slag to 1.0 or more, the strength of the molten slag can be increased to such an extent that no collapse or wear occurs when used as fluid particles. Moreover, by setting the basicity to 2.0 or less, it is possible to prevent a decrease in crystallinity and maintain a sufficient strength.

  Moreover, by setting the basicity of the molten slag to 1.2 or more, the crystallinity of the molten slag becomes high and the strength becomes sufficiently high, and the optimum strength as the fluidized particles can be secured. By setting the basicity of the molten slag to 1.5 or less, the melt viscosity of the molten molten slag does not become excessively high and can be smoothly discharged from the discharge port of the waste gasification melting furnace. In addition, the fluidity of the molten slag can be secured. That is, it is not necessary to excessively increase the molten slag discharge temperature (steaming temperature) (for example, 1500 ° C. or higher) in order to reduce the melt viscosity of the slag. Therefore, the temperature around the discharge port of the waste gasification melting furnace does not become excessively high, and an increase in wear of the refractory can be avoided. Moreover, since the molten slag discharged | emitted does not become high temperature excessively, a molten slag can be granulated to a favorable particle form.

The degree of the effect of preventing agglomeration depends on the composition ratio of each component of SiO ₂ , K ₂ O, and CaO of the SiO ₂ —K ₂ O—CaO compound generated on the surface of the fluid particles. A specific description based on the composition ratio will be described later with reference to FIG.

  Hereinafter, the operation of the circulating fluidized bed furnace 1 will be described focusing on the combustion of the oil palm empty fruit bunch in the riser 10. In the circulating fluidized bed furnace 1, molten slag having adjusted basicity is charged into the riser 10 as fluidized particles. In the riser 10, air is blown into the furnace from the diffuser tube 11 and the secondary air blowing port 12, thereby fluidizing the oil palm empty fruit bunches supplied into the riser 10 together with the fluidized particles. In the process, the oil palm empty fruit bunches are burned in the fluidized bed.

  Specifically, the fluidized particles are brought into a fluidized state by primary air blown from below in the riser 10 to form a concentrated layer of fluidized particles in the lower part of the riser 10, and have a high heat capacity and stirring effect possessed by the fluidized particles. Accelerates the drying and volatile release of oil palm empty fruit bunches. In addition, a thin layer of fluidized particles is formed in the upper portion of the riser 10 by blowing primary air and secondary air, and the oil palm empty fruit bunches are burned by the heat capacity and stirring effect of the fluidized particles. Do. That is, such a circulating fluidized bed furnace 1 prevents the generation of char (unburned carbon content) by forming a fluidized bed composed of a thick layer and a lean layer of fluidized particles in the riser 10, thereby improving efficiency. The oil palm empty fruit bunch is burned. Moreover, the combustion area | region in the riser 10 is maintained at about 850-900 degreeC.

  The exhaust gas generated by the combustion of the oil palm empty fruit bunches in the riser 10 is supplied to the collection unit 21 of the downcomer 20 through the connection pipe 30. A part of the fluid particles (molten slag) is also supplied to the collection unit 21 together with the exhaust gas. The collection unit 21 captures fluid particles, ash having a relatively large particle size, and the like and separates it from exhaust gas and ash having a relatively small particle size. Therefore, the molten slag as fluidized particles has a particle size suitable for circulation in the circulating fluidized bed furnace, and is suitable for capture by the collection unit 21 (for example, 70 μm to 1 mm). It is preferable that If the particle size of the molten slag is smaller than 70 μm, it is not suitable because it is not captured by the collection unit 21 and is sent to the exhaust gas treatment facility while being contained in the exhaust gas and is not recovered. If the particle size of the molten slag is larger than 1 mm, it may be difficult to flow in the circulating fluidized bed furnace, which is unsuitable. The exhaust gas separated by the collection unit 21 is accompanied by ash having a relatively small particle size, is sent from the upper part of the collection unit 21 to the exhaust gas treatment facility, and is discharged from the chimney after dust removal. Fluid particles collected by the collection unit 21 and ash having a relatively large particle size are returned to the lower portion of the riser 10 via the seal unit 23 and the return pipe 22.

In the present embodiment, the oil palm empty fruit bunch burned in the riser 10 releases gaseous potassium compounds in the combustion region. Further, the calcium compound fine particles are detached from the molten slag flowing particles. If silica sand particles are used as the fluidized particles, the gaseous potassium compound is adsorbed on the surface of the silica sand particles, and the melting point of the SiO ₂ —K ₂ O compound of 800 ° C. or lower which is lower than the furnace temperature. Is generated and a melt exists on the surface of the silica sand particles, and the silica sand particles are fused to each other. On the other hand, by using molten slag as fluidized particles as in this embodiment, fine particles containing a calcium compound coexist, so that the fine particles are melted containing silicon oxide that has been adsorbed with potassium compounds and started to produce a melt. It adheres to the surface of the slag fluidized particles, and a SiO ₂ —K ₂ O—CaO compound is generated as a reactant. The melting point of this reaction product is 1000 ° C. or higher, which is higher than the furnace temperature, and since there is no melt on the surface of the molten slag fluidized particles, fusion / aggregation of the molten slag fluidized particles can be prevented. Since the supply of the calcium compound continues on the surface of the molten slag fluidized particles where the melt has started to form, the melting point of the reactant which is the SiO ₂ —K ₂ O—CaO compound is maintained to be higher than the furnace temperature. The In this way, by using molten slag as fluidized particles, it is possible to suppress the formation of a melt by the potassium compound released from oil palm empty fruit bunches on the surface of fluidized particles, and prevent fusion / aggregation between fluidized particles. it can.

  As described above, in this embodiment, by using the molten slag as the fluidized particles, the fluidized particles are prevented from being fused and agglomerated, so that the fluidized particles are not agglomerated at the bottom of the furnace body of the riser 10. Therefore, the fluidized particles flow well, the normal operation of the circulating fluidized bed furnace 1 can be maintained, and the oil palm empty fruit bunch can be stably burned. In addition, problems such as generation of harmful gases such as NOx, damage to refractories in the furnace, shortening of the service life, generation of CO, and the like due to hot spots that are local high-temperature portions can be avoided.

  Further, as described above, in this embodiment, the fluid particles are prevented from fusing and aggregating with each other, so that the fluid particles are frequently extracted and replenished with new fluid particles, which has been frequently necessary to maintain the fluid state. No need. Therefore, the circulating fluidized bed furnace 1 can be reliably and continuously operated, and the generation of costs due to the frequent purchase of new fluidized particles and the disposal of the extracted fluidized particles can be prevented.

  Moreover, if alumina or the like is used as the fluidized particles, it is possible to avoid fusion / aggregation between the fluidized particles without supplying an additive, but fluidized particles such as alumina are expensive, and accordingly, Expense increases. On the other hand, in this embodiment, since an inexpensive molten slag can be used as fluidized particles by adding a small amount of additive, the cost can be reduced as a result.

In the present embodiment, the molten slag used as the fluidized particles is the pyrolysis residue molten slag, but the molten slag as the fluidized particles is not limited to this. For example, the waste ash is melted in an ash melting furnace. Then, it may be ash melt slag generated by cooling. The main components of the ash molten slag are silicon oxide (SiO), calcium oxide (CaO), and about 10 to 30 wt% alumina (Al ₂ O ₃ ), and contain calcium oxide (CaO). Similar to the residual molten slag, it is suitable as fluidized particles for preventing agglomeration when burning herbaceous biomass.

  When using ash molten slag as fluidized particles, the basicity of the ash molten slag is adjusted by adjusting the supply amount of quick lime or limestone supplied together with the incinerated ash that is the object of melting treatment in the ash melting furnace. be able to. In addition, the basicity of the ash molten slag is determined by the alkaline fly ash containing limestone or slaked lime that is blown into the exhaust gas and collected together with the fly ash in the dust collector for the removal of the acidic gas in the exhaust gas from the incinerator. It can also adjust by supplying with the incinerated ash which is a fusion process object in an ash melting furnace, and adjusting the supply amount of the said alkali fly ash. In this way, by adjusting the supply amount of limestone, quicklime and alkali fly ash in the ash melting furnace and adjusting the basicity of the ash molten slag within a predetermined range, the ash molten slag is effectively used as fluidized particles. be able to.

  Thus, when adjusting the supply amount of quick lime, limestone or alkali fly ash to the ash to be treated in the ash melting furnace and setting the basicity within a predetermined range, in response to the increase in viscosity accompanying the increase in basicity of the molten slag In order to raise molten slag discharge temperature, increase the amount of heat given for ash melting by electrical resistance, plasma heating, coke combustion, etc., raise the temperature of the molten slag, and have a composition suitable for flowing particles The slag adjusted to (basicity) can be discharged smoothly. Further, since the melting point of the molten slag is increased by adjusting the basicity of the molten slag, the slag discharge temperature (steaming temperature) is set to 1350 to 1500 ° corresponding to the increase of the melting point so that the slag is discharged smoothly. And Then, the discharged molten slag is dropped into a water tank and granulated or air cooled, and the particle size of the cooled slag is adjusted by grinding treatment to produce molten slag particles having a preferable particle size range.

  Moreover, although this embodiment demonstrated the form which applied this invention to the circulating fluidized bed furnace, not only this but this invention is applicable also to the fluidized bed furnace which does not have a downcomer.

  Next, the prevention of agglomeration will be described with reference to FIG. 2, focusing on the composition of the compound produced in the fluidized bed furnace.

FIG. 2 shows the composition of each component of SiO _2, K ₂ O, and CaO when potassium liberated from biomass enters molten slag containing SiO _{2 and} CaO as components to generate a SiO ₂ -K ₂ O—CaO compound. The relationship between the ratio and the melting point temperature is represented by the three-phase diagram of SiO ₂ , K ₂ O, and CaO (Roedder, E. (1959) Silicate Melt Systems. Physics and Chemistry of the Earth, Vol. 3., pp.224-297. It is a figure shown based on.).

The molten slag having SiO _{2 and} CaO as components and having a basicity (CaO / SiO ₂ weight ratio) of 1.2 is a composition at the position of ◯ in the figure, and the melting point temperature is 1500 ° C. Potassium liberated from biomass hardly penetrates into the molten slag having this composition, but when potassium penetrates in a high-temperature flame or the like, the composition of the SiO ₂ -K ₂ O—CaO compound is on the line from the position of ○. As the K ₂ O ratio increases, the composition of the position progresses on a straight line toward the position showing 100% K ₂ O. Even if potassium intrudes until the composition of K ₂ O reaches about 30%, the melting point is 1500 ° C., the melting point temperature of the SiO ₂ —K ₂ O—CaO compound does not change, and no melting point drop occurs. Therefore, it is clearly shown that the fluidized bed furnace at a furnace temperature lower than 1500 ° C. does not enter a molten state and does not cause fusion / aggregation of fluidized particles.

1 Circulating fluidized bed furnace 10 Riser (furnace body)
21 Collection part 22 Return pipe

Claims (7)

The biomass is supplied to the furnace body of the fluidized bed furnace and the oxidizing gas is supplied from the lower part of the furnace body to flow the biomass together with the fluidized particles to form a fluidized bed, and the biomass is burned in the fluidized bed. In the combustion method
Pyrolysis residue melting slag produced by melting the pyrolysis residue of the waste in the waste gasification melting furnace or cooling, or by melting the ash of the waste in the ash melting furnace and cooling A method for burning biomass characterized in that ash molten slag is used as fluidized particles. Biomass according to claim 1, basicity (CaO / SiO ₂ weight ratio in the slag) is to be used as flowing particles adjusted pyrolysis residue molten slag or ash molten slag to 1.0 to 2.0 Combustion method. The biomass according to claim 1, wherein pyrolysis residue molten slag or ash molten slag whose basicity (CaO / SiO ₂ weight ratio in slag) is adjusted to 1.2 to 1.5 is used as fluidized particles. Combustion method.   When using pyrolysis residue melt slag as fluidized particles, the basicity of pyrolysis residue melt slag will be adjusted by adjusting the amount of limestone supplied with waste in the waste gasification melting furnace. The method for burning biomass according to claim 2 or claim 3.   When using ash melt slag as fluidized particles, the basicity of ash melt slag will be adjusted by adjusting the amount of quicklime or limestone supplied with the incinerated ash that is the subject of melting treatment in the ash melting furnace. The method for burning biomass according to claim 2 or claim 3.   When ash molten slag is used as fluidized particles, alkaline fly ash containing limestone or slaked lime that has been blown into the exhaust gas and collected together with fly ash by the dust collector to remove acidic gas in the exhaust gas from the incinerator The basicity of molten slag is adjusted by supplying with the incinerated ash which is a fusion processing object in an ash melting furnace, and adjusting the supply amount of the said alkali fly ash. Biomass burning method. Biomass having a furnace body of a fluidized bed furnace in which an oxidizing gas is supplied from the lower part and biomass is flowed together with fluidized particles to form a fluidized bed, and the biomass is combusted in the fluidized bed. In the combustion apparatus of
The above fluidized particles are obtained by melting the pyrolysis residue of the waste in the waste gasification melting furnace and then cooling it and melting the ash of the waste in the ash melting furnace. A biomass combustion apparatus characterized by being ash molten slag produced by cooling.

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